Recent evidence has shown that early life exposure to cats and dogs in the home may protect against allergic sensitization and asthma in certain communities. This pet protective effect, however, has not been extensively studied either in the inner city or in a setting where children are exposed to high levels of cockroach and mouse allergen. An ongoing birth cohort study currently being conducted in northern Manhattan by the Columbia Center for Children's Environmental Health offers an ideal opportunity to study this phenomenon in an inner-city community. We hypothesize that for children living in the inner city exposed to cockroach and mouse allergens, exposure to high concentrations of cat and dog allergens early in life decreases the risk of developing pet-specific IgE responses and allergic symptoms. This hypothesis is based on a protective effect of pet ownership observed elsewhere, and a discrepancy in the reported general atopy protective effect reported in communities without the major allergen, dust mite (e.g., Sweden), but not observed in communities with a significant mite population (e.g., New Zealand). The specific aims are designed to elucidate the role of high dose cat and dog allergen exposure in the development of allergic disease in inner-city children, commonly exposed to cockroach and mouse allergens: 1) Determine the level of pet allergen in the home over multiple time-points and validate the data with questionnaire data. This will allow us to better quantify cumulative pet allergen exposure. 2) Determine the early life allergen specific antibody responses relative to pet ownership in this community. We will compare IgE and IgG responses to cat and dog with Reponses to other allergens. 3) Determine whether pet allergen exposure in an inner-city community is associated with early predictors of allergic disease and asthma including persistent wheeze, doctor diagnosed eczema and asthma symptoms.